Default Template – Changing width of the content

I am using the default template and would like to get the content wider (more to the left) and keep the menu where it is. I know I’m going to have to edit the header also in the style.css file along with the images, but don’t know what to change and how.
I’ve done some searching, but haven’t found my answer, most replies tell people to just get a new temptale which I am not planning to do.
Here’s what I want it to look like. https://img8.picsplace.to/img8/16/wider.jpg
link to my blog – https://www.facethemusik.net/
Please help me out